PEOFESSOE  TINDALL  ON  SOME  PHYSICAL  PEOPEETIES  OP  ICE. 
213 
9.  Pieces  of  ice  were  therefore  prepared,  through  which  the  sunbeams  were  sent  so 
as  to  develope  the  flowers  in  considerable  quantity  and  magnitude.  These  pieces  were 
then  dipped  into  warm  water  contained  in  a glass  vessel,  and  the  effect,  when  the  melt- 
ing reached  the  bright  spots,  Avas  carefully  observed  through  a lens.  The  moment  a 
liquid  connexion  was  established  between  them  and  the  atmosphere,  the  apparent  bubbles 
suddenly  collapsed,  and  no  trace  of  air  rose  to  the  surface  of  the  warm  water. 
10.  This  is  the  result  which  ought  to  be  expected.  The  volume  of  water  at  32°  being 
less  than  that  of  ice  at  the  same  temperatm’e,  the  formation  of  each  flower  ought  to  be 
attended  with  the  formation  of  a vacuum,  which  disappears  in  the  manner  described 
when  the  ice  surrounding  it  is  melted. 
Similar  experiments  were  made  with  ice  in  which  true  air-bubbles  were  enclosed. 
When  the  melting  liberated  the  air,  the  bubbles  rose  slowly  through  the  liquid  and 
floated  for  a time  upon  its  surface. 
11.  Exposure  for  a second,  or  even  less,  to  the  action  of  the  sun  was  sufficient  to 
develope  the  flowers  (4)  in  the  ice.  The  first  appearance  of  the  central  star  of  light 
was  often  accompanied  by  an  audible  clink,  as  if  the  substance  had  been  suddenly  rup- 
tured. The  edges  of  the  petals  were  at  the  commencement  definitely  curved  thus ; 
; but  when  the  action  was  permitted  to  continue,  and  sometimes  even  without 
this,  when  the  sun  was  strong,  the  edges  of  the  petals  became  serrated  thus : 
the  beauty  of  the  figure  being  thereby  augmented. 
Sometimes  a number  of  elementary  floAvers  grouped  together  to  form  a thickly-leaved 
cluster  resembling  a rose.  Here  and  there  also  amid  the  flowers  a liquid  hexagon  might 
be  observed,  but  such  were  of  rare  occurrence. 
12.  The  act  of  crystalline  dissection,  if  I may  use  the  term,  thus  performed  by  the 
solar  beams,  is  manifestly  determined  by  the  manner  in  which  the  crystalline  forces  have 
arranged  the  molecules.  By  the  abstraction  of  heat  the  molecules  are  enabled  to  build 
themselves  together,  by  the  introduction  of  heat  this  architecture  is  taken  down.  The 
perfect  symmetry  of  the  flowers,  from  which  there  is  no  deviation,  argues  a similar  sym- 
metiy  in  the  molecular  architecture ; and  hence,  as  optical  phenomena  depend  upon  the 
molecular  arrangement,  we  might  pronounce  with  perfect  certainty  from  the  foregoing 
experiments,  that  ice  is,  what  Sir  David  Brewster  long  ago  proved  it  to  be,  optically 
speaking,  uniaxal,  the  axis  being  perpendicular  to  the  surface  of  freezing. 
§11. 
13.  On  the  25th  of  September,  while  examining  a perfectly  transparent  piece  of 
Norway  ice,  which  had  not  been  traversed  by  the  condensed  sunbeams,  I found  the 
interior  of  the  mass  crowded  with  parallel  liquid  disks,  varying  in  diameter  from  the 
tenth  to  the  hundredth  of  an  inch.  These  disks  were  so  thin,  that  when  looked  at  in 
section  they  were  reduced  to  the  finest  lines.  They  had  the  exact  appearance  of  the 
